Carburetor



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CARBURETOR S. F. HUNT original Fiied June 17, 1945 July l, 1952 Patented July 1, 1952 UNITED* STATES` PATENT ori-ICE` l CARBURETOR Scott F. Hunt, Meriden, Conn., assignor to Niles- YBement-Pond Company, acorporation of New Jer West Hartford, Conn.,

Sey y 1 'originarapplicationune v17, 1943, serial No.

491,096; now Patent N0. 251142,046,v

dated May 25, '1948.' Divided and this application November 20, 1947, Serial No. 787,101

, 1 8 Claims.

Thisis a divisionvof -my co-pending application, Serial No. 491,096, filed June 17,1943, entitled Carburetorsfand matured-into Patent No. 2,442,046, issued May25, 1948.

This invention relates-fto carburetorsvfor internal combustion jen'gines,v and particularly to means for operating such carburetors so as to provide improved acceleration characteristics of the engine.

"'It has previously been-'proposed to provi'de,rin alcarburetor for an duction system ata point downstream from 'the throttle, and effective' upon an4 increase in such pressurasuch as'accompanies a sudden opening movementofthe throttles; to inject into the air stream an additional ly accelerate the engine; j Y

It has been' found ,thatu litlNr-deyices` of the type described; thefadditional supply'offuel provided;- is notalways' s'uic'ient to complete the acceleration ofthe engine' .to a'speedcorresponding to the new throttle position.' Such* a device provides a momentary additional supply of fuel for the en gine, but it has been found thatthis additional supply of fuel may be completely dissipated before the acceleration'of the vengine iscompleted.

:It yistherefore an object of the vpresent invention 'to provide'improved means for supplying additional fuelt an internal combustion engine durin'gacceleration Vof' theengine'I A further object 'ofthe' invention 'is to provide an improved fuel V'supply'` system .for an internal combustion` enginewherein rst'fdevice is used to give anincreased "fuelsupply immediately inreksponse to acceleration of .the engine, and asecwhich'fmans are' provided .to increase the pres;l sure on thefuel ow controlling valver in response to 'accelerationoflthe engine on'which the .carburetris used. f. f Another-object of the `ip re'sent invention is to provlde, in acarburetor of the type 'described; a

internal' combustion engine, a device responsive tothe pressurein the air vin--A supply of fuel'so as to rapidl 51; the increased pressure operated device which respondsto `an` manifold pressure to sup-r ply an additional amountof fuel to the engine,.

increase in the intake and which operates cumulatively in response to y y fuel supply to further increase the supply 0f fuel.

A further object of the invention is to providey an improved pressure controlling device which is balanced against the controlled pressure so that '103 upon the applicationof a! force to the pressure controlling device,y it operates throughout its range of movementwithout being retarded by;

changes in the controlled pressure.

A further object of the invention is to provide, in a carburetor having a throttle controlling the 110W of air, means responsive to the pressure downstream vfrom the throttle for supplying additional fuel tov ,thel engine upon acceleration thereof, and means for balancing the pressure zu) responsive means against changes in atmospheric A furtherbjerctff' the present iventiqn is to f supplying additional provide improved means for fuel to an internalcombustion engine'upon acceleration, comprising a valve connected in parallel withV a fuel regulating valve and controlled as an incident to acceleration of lthe engine. A.- still further objects toployide, rin such'angar-v rangement, a... fuel reservoir havingv an outlet controlled. by anacceleration responsive valve andan acceleration responsive pump for vempty-v ing the reservoir. A'istillfurther object is to provide such an" arrangement in which the valve is maintainedopen than that required reservoir.

vOther objectsand advantages .Hof the present invention will becomev apparent from a consideration:Y of vthe appended specification, claimsand drawing which illustrates, somewhat dia-v grammatically, an aircraft carburetor embodying certain principles of my invention.

There snshown in the drawing a carburetor body portion `I including an air passage generally indicatedl atvt. Air `Venters the passage atan inlet.3, vflows thru-a Venturi restriction 4, pastJ a dischargeY nozzle BA to an out-* A secondair, passage connects the air inlet-31;. and :the throat of venturi 4. Thissecond ain passage may be rtraced from the inlet 3V thru av plurality of impact tubes, a vent ringe. ak conduitv l0, an expansibleichamber Il, a restriction I 2 an expansible chamber I3, apconduit [4f a valve Lchamber l5, and @conduit ls to the throat' for a period of time longer: for the -pump to empty the system 3 I.

CII

described in connection with bellows |35 of my aforementioned Patent The chambers Ii and unit I8, which includes a casing 28 separatedby a pair of transverse diaphragms'l and 22. intoA A motion expansible chambers II, I3 and 23. transmitting member 2d is attached to the center of diaphragm 2I, and acts lageivinstthe center of diaphragm 22.

25 in the housing 20. A spring 25 biases the member 2d toward a position wherein the port 25 is closed by the diaphragm 22.

f The fuel` supply to the carburetor passes from a pump or other source of fuel under pressure (not shown) thru a conduit 21, a uelregulator unit 2B, a conduit 25, a mixture control unit 30, a jet system 3 I,`a, conduit 32, a pressure regulator 33, and a conduit 34 to the discharge nozzle E.

- The fuel regulator unit 28 comprises a housing 35 separated by a diaphragm 38 into a pair cf expansible chambers 31 and 38. The diaphragm 36 carries at its center a balanced valve-38,which.

controlstheflow of fuel from the conduit 21 thru the chamber 33 to the conduit 29. A compression spring 43 biases the valve 39 for movement toward open positions f The position-'of valve 39 is determined by the difference between'pressures in the chambers 31 and 38 -andiby the force exerted by the spring 48. The chambers 31 and 33 arel connected by A portion of fuel ventering the chamber 38 hows thru the restriction 4I, chamber 31. a conduit 42; -pa'st va valve 43, thru -a conduit 44, a check valve'45, a conduit '46, expansible chamber 23 off the'meter-ing unit I9, and a conduit 41 to an'ope'ning 48 in thev walll ofsair passager.y

The checkyalve '45 permits a flow thru the conduit' justtraced in a direction from the iuel regulator unit 28 to the pressure meter ISL The mixture control unit 30 includes a discv valve 49 fixed on a shaft58.` The shaft 50 may be manually rotated, by means not shown, so that thefdisc '49 controls the flow of fuelffrom the 'conduit 29 to a pairk of conduits"5| and 52 leading to the jet system 3l. When the shaft 58 is in aposition so that fuel can flow only thru the conduit 52 and not thru conduit 5I, the mixture control is said to be in the lean position. When the disc valve 48is in a position such that fuel can flow thru both conduits I and 52, the mixture control is said to bei'n the rich position. o

The conduit 52 conveys fuel to a pair of restrictions .53 and 54 in the jet system 3I.. The restriction 53 is fixedY 'and the restriction 54 is normallyv closed by. a valve 55 to closed'A position by a 'spring 56.' 5I conveys fuel -thru arestriction A571 inth'e jet l All fuel passing thru the restrictions54 and 51 must pass thru another restriction 5`B"before emerging from the jet system into the conduit 32.' Y

The pressure regulator unit 33 comprises 'a' casing 58 divided by aflexible diaphragm (il)Y into a pair p of expansible I3 are part of a metering' The center of diaphragm -22 p is thereby moved to close or open a valve port.

which is biased. The f conduit;

v chambers B'I andtz.. Ther cond'uit`32:` is connected'to the chamber 62, and.

Amoves within the cylinder y spring 82, located in the cylinder 80, biases'the The passage 85 is of smaller Lsible chambers 11,12, 1a

vtition 88 vlies between and parallel to the diatinues, a :point is reached `where a balanced valve 63 attached to the center of the diaphragm 60 controls the passage of fuel from the chamber B2 to the conduit 34. A compression spring 84 biases the valve B3 toward its closed position. A conduit 65 connects the-chamber El to the conduit wand thence tothe vent ring 3.

An acceleration control unit is generally indicated at 68. This unit includes a casing 61 which is divided by a rigid partition 68 and a pair of flexible diaphragme 89 and 18 into four expanand 14. The rigid parphragms B9 and 10. The diaphragms 69 and 18 are connected by a rigid force transmitting meml ber 15, which is biased upwardly by a compression spring 16.

f The chamber 14 is connected thru a conduit 11 with the conduit 29, so that the chamber 14 receives fuel at the pressure existing downstream from the fuel regulator 28. The chamber 13 is connected thru a conduit 18 and conduits and I8 to the vent ring lil, so that the chamber 13 is supplied with air at impact pressure. The chamber 12 is connected thru a conduit 19 to a point in the air passage 2 downstream from the throttle 5.

The chamber 1I is connected to the'conduit 42 thru acylindrical chamber 80. The valve 431s' supported by a piston 8I, which may be formed integrally with valve 43, as illustrated, and ,whichv 88. A compression piston BI Vto the position shown in the drawing, wherein the valve 43 is separated'from its seat 83.

The piston 8I is bored at its center to provide a passage 84. Another passage 85 is bored thru the valve 43 inv alignment with the passage 84,.

diameter than passage 84. A laterally extendingA passage 86 is bored thru thesde of valve member 43,andv intersects thepassages 84 and 85. VThe lower end of cylinder 8 0 is closed by av xed plug 81.y The plug 81 is provided with a conical projection 88 in the. center of its upper surface, in alignment with passage 84 in piston 8I. A narrow passage 89 is bored thru the plu'gi81 to the apex of the conical projection 88. A plurality of larger parallel passages 98 are bored thru the plug 31; rFhev when the piston Aill is `fuel"iiowing into the iiuid being dischargedcan'flow thru the parallel" passages 89 and 58. VHence theuid in chamber 1I can be discharged faster than the chainber can be lled. p il Operation' The operation of the carburetor shown will first be considered under conditions of constant throttle position, so that unit 66 is not operating. Under these conditions,

the pressure differential established between'the throat of venturi 4 is communie.

inlet 3 and the cated to the chambers II andrI3 of meteringunit I9. `This pressure differential acts upwardly on,

the. member 24, and .therefore tends to move they diaphragm 22 in a direction to close theport 25.

This upward force is opposed by the pressureor; As the*I nember24- the port 25 becomes more re-r stricted, yand the pressure in` chamber.;23winv`-- the fuelin the chamber 23. moves upwardly,

creases. .As the movement,A ofv member 24 conthru thefgnarrow passage' the :acceleration control.

force due to the pressurein chamber 23 balances that due to the pressure'differentialbetween the chambers I and |3, andthe member 21| .remains in that position. It' may therefore be seen that a pressure is established in chamber 23-whichis a'measure of the massof air flowing thru the passagev. This pressure inl chamber 23 is communicated back thru conduit 43, check valve 45,1 conduit 44, past lvalve 43 and thru conduit 42 to.Y

chamber 31 of the fuel regulatorZB.

The pressure in chamber 31 'acts on the valve 39 in an opening direction, being aided by the spring 49 and'opposed by the .pressure in chamber 3B. As the valve 39 is moved by a change in the pressure in chamber31, the pressure in chamber 38 -is varied in a sense to oppose the pressure change in chamber 31. 'I'herefore as the movement of valve 39 continues, a position is reached at which the pressures in chambers 31 and 38 balance each other and the-force of spring 40, and the valve 39 remains in that position. It may therefore be seen that the fuel ow thru the valve l39 is regulated in accordance with the pressure in chamber 31, which is in turn controlled by the mass of air flowing thru the pas-V sage 2.- l Y The mixture control unit is provided to permit the operator of the aircraft in which the carburetor is installed, to `select either arich or lean mixture, dependingupon the conditions underwhich the aircraft is operated. The mixture control unit also may be used vby the operator kto completely cut olf the supply of -fuel to `the carburetor when it is desired to stop the engine.

- The jet systeml3| provides a fixed restriction in theffuel line. In accordance with well-known hydraulic laws, the flow thru such a xed restriction is a function of the pressure differential across it. The pressure regulator 33, as described in more detail below, operates to maintaina Asubstantially constant outlet pressure on the jet systemv 3|. Therefore the fuel flow thru the jet system, and hence the flow to the carburetor is controlled by the fuel regulator unit 28, which` establishes the fuel pressure on the inlet side ofY the Vjet system 3| as a function ofthe air ilowthru` the passage 2. l The'v'a'lve 55 operates to automatically .enrich the mixture supplied to the `engine under conditions of relatively heavy load. Such vheavy load conditions are accompanied by high rates'of air flow thru the passage 2, which in turn cause a high pressurel diiferentialv across' the jet`lsystem 3|. When this pressure-v differential exceeds a value determined by the strength of spring 56, the

valve 55 opens, thereby increasing the quantity of fuel flowing in proportion a1r. Y

VIn the pressure regulator unit 33, the pressure inchamber 62 is balanced against the pressure in chamber 6| and the force of spring lili.' The pressure in chamber 6| is relatively low compared to that is chamber 32 and to the force of spring 64. Therefore the variations of pressurein 6| have'relatively'little regulatingeifect on the positionof` valve 63,- andthe unit operates to'fmain` tain av substantially constant pressure inl chamber 62.`A Since the valve 63 is balanced against the pressure at its outlet, the variations in presto the quantity of sure adjacent the discharge nozzle 6 are prevented from affecting the quantity of fuel-sup- Ypliedtothe engine.l VThe connection of chamber 6| throughconduit'65 to vent ring 9 is chiefly for thejpu'rpose of venting the chamber V6| -soas to permitready movement of the valve 63. =It will befapparent, howeveigthat changes in; atmospheric pressure do affect theoperation of valve 63 to some extent. An increase in atmospheric pressure, for example, increases-the pressure in chamber. 6|, thereby decreasing'the fuel ow thru the'j'et system 3|. Likewise, a decrease in atmospheric pressure causes an increased fuel flow. 'Ihis effect may be taken into account in designing thealtitude compensating valve |1.

vConsidering the operation of the acceleration control unit 66, it may be seen that the chamber 1| is normally lled with fuel received thru the passage 84; .Under part throttle conditions the pressure Y in chamber 12 is considerably below atmospheric, and tends to maintain diaphragm 69 near the bottomV of chamber 12. Upon an openingmovement of thethrottle 5, the pressure inthe chamber 12issuddenlyincreased, and acts upwardly'on the diaphragm 69, thereby forcing the pistoritill upwardly and moving valve 43 into engagement l'with its seat 83, and discharging the fuel inthev chamber' 1I thru the passages 89. 90 and 84.' Some of thisl fuel flows on thru passage 85 and the remainder flows thru passage 86 and the conduit 42-into the chamber 31 of fuel regulatcr unit 28'.- `Ths increases the pressure in the chamber 31`an'd causes an opening movement of the valve 39 so as to increase the supply of fuel to theengine, and' to provide a balancing increase of pressure in chamber 38. The increase of pressure infchamber38 is communicated thru conduit 11 to chamber 14'; thereby applying a cumulative force on the diaphragm 69 Iacting in a direction to more' `rapidly empty the chamber 1| and to further increase the pressure inchamber 31. As soon as valve 43 kengages its seat 83; the metering `unit'f'lil no longer controls the pressure y injfchamber 31', butthe latter pressure is controlled byithe acceleration control unit 66 alone. This control continues until the chamber 1| is compl'etely.v empty,jwhereupon the fuelin chamber 31 startsfflowing thru the passages 86 and 85 to conduit 4'4` andmetering ,unitv I9 is again restored to control. As'lo'rig 'as' the pressure in chamber 31 is controlled by the acceleration control unit'66, the supply of fuelto the engine is increased beyond its norrnal proportion, thereby causing more rapidac celeration to the speed called for by the new .throttle position. This increased fuel supply islsometimes called a boosting action.

When the'throttle .5 is moved toward its closed` position,` the Apressure onthedownstream side of it decreases, -rthereby causing a downward movement Yof diaphragm- 69. f 'I'he pressure underpiston.8|;.is ,thereby reduced, and it is again moved tofthe position shown inthe drawing. The chamber -11| thenlslowly lls .with fuel thru the passages 85 and 86 in parallel, and 84 and 89. This decreases the pressure in chamber 31, which causes diaphragm 36 to operate valve 39 to decrease the pressure in chamber 38. The decreased pressure in-chamber 38 is communicated thru conduit 11 too small or too great. Vthe engine will not decelerate rapidly enough, or will decelerate too much.

During the accelerating phase of operation of the control unit S6, the difference between the cross-sectional areas of the passages 86 and 85 determines the amount of the increased fuel supply, since that part of the fuel discharged from chamber 'Il thru the passage 85 has no effect on the quantity of fuel supplied to the carburetor. Hence. as the size of passage 85 is increased with respect to that of passage 86, the amount of the increased fuel supply to the engine is reduced.

During the decelerating phase of operation of the control unit E8, the magnitude of the decrease in the fuel supply is determined by the sum of the cross-sectional areas of the passages 85 and 86, since fuel flows thru both in parallel. Hence, by increasing the size of passage 85, the robbing action is increased. Similarly, a decrease in the size of passage 85 decreases therobbing action.

The duration of the boostingY action and the duration of the robbing action are both affected similarly by a change in the size of any of the passages 84, 85 and 88. The relative duration of the boosting and robbing actions are determined by the relative sizes of the passages 89 and 9D.

The check valve d is provided to prevent the suction in chamber All during the lling operation from being communicated to the chamber 23 so as to turn the diaphragm 22 inside out. If the check valve 45 were not provided, the operation of diaphragm 22 in that manner might cause it to wear out quickly.

rIhe chambers 1I and 14, Whose internal pressures act in opposite directions on the member 15, are respectively connected to chambers 31 and 3S of the fuel regulator 28. Any pressure change in chamber 31 is accompanied by a parallel change in chamber 38. Therefore, it may be seen that the operation of member is not affected by variations in the pressure of the fuel source, or by any variation in pressure in chambers 3l and 38.

Also, since the chamber 13 is connected thru conduits 18 and l0 to vent ring 9, it is subject to changes in atmospheric pressure. Such atmospheric pressure changes are also effective to vary the pressure in chamber "l2, where they act ,Y

in a direction opposite the-effect produced in chamber 1S. Therefore the action of acceleration control unit 66 is balancedfagainst the effects of variations in atmospheric pressure. l

While I have shown and described the preferred embodiment of my invention, other modifications thereof will occur to those skilled in the art, and I therefore intend that my invention shall be limited only by the appended claims.

I claim as my invention:

l. In a `carburetor for an internal combustion engine, in combination, a source of fuel under superatmospheric pressure, a conduit for conveying fuel to said engine, valve means actuated solely by variations` lof fuel pressure for controllingLthe flow of fuelf thru said conduit, throttle means for controlling the flowrof air thru said carburetor, means responsive to thejair pressure at a point downstream from said throttle means hydraulically connectedto said valve means for varying the fuel pressure applied to said valve moansrand effective upon an increase in said air pressure to vary said fuel pressure in a sense to increase the ow of fuel thru :said valve means, and means for counterbalancing the effect of variations in atmospheric pressure on said air pressure responsive means.

2. In a carburetor for an internal combustion engine, in combination, a source of fuel under superatmospheric pressure, a conduit for conveying fuel to said engine, valve means actuated solely by variations of fuel pressure for controlling the flow of fuel thru said conduit, throttle means for controlling the flow of air thru said carburetor, means responsive to the air pressure at a point downstream from said throttle means and hydraulically connected to said valve means for'varying the fuel pressure applied to said valve means and effective uponl an increase in said air pressure to vary said fuel pressure in a sense to increase the flow of fuel thru said valve means, means for counterbalancing the effect of variations in said fuel pressure on said valve means, and means for counterbalancing the effect of variations in atmospheric pressure-on said air pressure responsive means.

3. In a carburetor for an internal combustion engine, in combination, a source of fuel under superatmospheric pressure, a conduit for conveying fuel to said engine, valve means actuated solely by variations of fuel pressure for controlling the flow of fuel thru said conduit, throttle means for controlling the flow of air thru said carburetor', meansresponsive to the air pressure at a point downstream from said throttle means and hydraulically connected to said valve means for varying the fuel pressure applied to said valve means and effective upon an increase in said Vair pressure to vary said fuel pressure in a sense to increase the flow of fuel thru said valve means, and `means for counterbalancing the effect of variations in said fuel pressure on said air pressure responsive means.

e. A fuel supply system for an internal combustion engine, comprising in combination, a source of fluid fuel, a rst conduit for `conveying fuel-from said source to said engine, a metering restriction in said conduit, valve means actuated solely by variations of fuel pressure for controlling `the fuel flow thru said conduit, passage means for conveying air for combustion purposes to said engine, means responsive to the quantity ofY air flowing thru said passage means separate from and normally connected only hydraulically to said valve Lmeans to control the operation of said valve means and thereby control said fuel fiow in proportion to said air flow, throttle means for controlling the flow of air thru said passage means, and means responsive to the air pressure in said-,passage means at a point downstream from said throttlemeans, hydraulically connected to said valve means and said air quantity responsive means, and effective upon an increasein said air pressure to remove said air quantity responsive means from control of said valve means and to operate said valve means to increase the fuel flow therethru;

5. Ina carburetor, in combination, throttle means for controlling the -flow of air thru said carburetor, valve means actuated solely -by variations-of fuel pressure for `controlling the flow of fuel thru said carburetor, means responsive to theairpressure atta point downstream from said throttleV means, hydraulically connected to said valve means, and effective upon an increase in said air pressure -to operate said valve means to increase Athe flow of fuel therethru, and means responsive to the `flow of fuel thru said valve meansfto cumulatively` increase said fuel flow.

"6, In a carburetor for an internal combustion engine, in combination, a conduit, means for supplying fuel under kpressure through said conduit .to said engine, valve means actuated solely by variations in fuel pressure for controllingk said fuel supply to. said engine, an expansble chamber havinga movable wall, passage means connecting said conduit and said chamber, means for balancing said wall against the effect of variations Ain pressure within said chamber, throttle means limit of its range of movement.

7. In a fuel supply system for an internal combustion engine, in combination, a first conduit for conveying air to said engine for combustion purposes, a second conduit for conveying fuel to said engine, a source for supplying fuel to said second conduit under superatmospheric pressure, means associated with said first conduit-I for producing two unequal pressures whose difference is a measure of the quantity of air flowing therethru, a metering restriction in said secondv conduit, means for controlling the pressure differential across said restriction to control the flow of fuel therethru, a third conduit supplied with fuel from said source and including a restriction, an expansible chamber connected to said third conduit and having a movable wall operatively connected to said pressure differential controlling means for positioning the same, valve means for Vcontrolling the flow of fluid thru said third conduit and thereby the pressure inr said chamber and the position of said pressure diil'erentialcontrolling means, means subjected to said two unequal pressures for operating said valve means in accordance with thedifference of said pressures, and means responsive to an increase in air pressure in said first conduit for additionally controlling the pressure in said chamber to move said pressure differential controlling means in a fuel flow'increasing direction.

8. In a fuel supply system for an internal combustion engine, a liquid fuel conduit, a vmetering restriction in said conduit, a main valve for regulating the pressure in said conduit on one side of said restriction, an expansible chamber having a movable wall subject on its external surface to the regulated fuel pressure in said conduit on said one side of said restriction, a restricted inlet passage connecting said chamber to said conduit, a restricted outlet passage connecting said chamber to a point maintained Yat a lower pressure, a connection between said wall and said valve for moving saidV valve in an opening direction when the pressure in said chamber increases, pilot valve means for controlling one of said restricted passages, means responsive to the rate of flow of combustion air to said engine for operating said pilot valve means, a throttle for controlling the flow of air to said engine, a pump operative to discharge fuel upon an opening movement of said throttle, an inlet conduit for supplying fuel to said pump, a discharge conduit for conveying fuel from said pump to said chamber, and a fixed restriction in said pump discharge conduit for retarding the increase in pressure in said chamber -10 and the consequentopening movementI of said valveV in response toi operationof said pump, the fixed restriction` in said pump discharge conduit delaying restoration of Asaid valve toits normal operating condition following' an operation 'of said pump.

9. A fuel supply system for an internal combustion engine, comprising in combination, means for supplying fluid vfuel under supera'tmospheric pressure, a first conduit forV conveying fuel from said fuel supply means to said engine, a metering restriction in said conduit, first valve means for controlling the fuel flow thru -said conduit, a first expansible chamber having a movablewall operatively connected to said first valve means for positioning thesame, a restricted inlet 'passage connecting said fuel conduit and said frstchamber, a restricted outlet passage for said chamber, second valvev means in' said outlet passage, passage means for conveying air for combustion purposes to said engine, means responsive to the quantity of air flowing thru said passage means to operate said second valve means. and'thereby to lcontrol said fuel flow in proportion to said air ow, throttle means for controlling the flow of air thru saidpassage means, a second Aexparisible chamber, a restricted passage connecting; said rst and second chambers, means responsiveito the airz'pressure in said passage means at fa-'po'int downstream from said throttle-means and effec.- tive upon an' increaseinsaid4 air pressure to con:- tra-ct` saidsecond chamberY and thereby supply additional fuel to said first chamberv soias to operate said first valvel means to increase the fuel flow therethru, and valve means operated as;l an incidentto vthe discharge of fluid fromsaid Vsecondchamber'to closesaid restricted outlet passage between said first chamber and said second valve means.

' 10. A'fuel supply system as in claim 9 including flexible diaphragm means forming apart of said operating means for said second valve means, and a check valve in said outlet passage between said rstchamber and said second valve' means for protecting said flexible diaphragm means by preventing reversal thereof due to the withdrawal of fuel froml said outlet passage upon expansion of said second chamber.

11. A fuel supply system as in claim 9 including means for counterbalancing the effect of variations in the fuel pressure downstream.y from said rst valve means on the expansion of said second chamber. y f

12. A fuel supply system as in claim 9 including means for counterbalancing the veffect of variations in atmospheric pressure on the expansion of said second'chamber. 1

13. A fuel supply'system` as in claim 9 includingmeans for counterbalancing the effect of vari-` ations in the fuel pressure downstream from said first valve means on the expansion of said second chamber, and means for counterbalan'cingthe effect of variations in atmospheric pressure. on the expansion of said second chamber.

14. A fuelisupply system for aninternal combusti'on engine, comprising in combination, means for supplying fluid fuel under superatmospheric' pressure, arst conduit. for conveying fuel fromVv said fuel supply means to saidengine, a metering restriction in said conduit, first valve means for controlling the fuel flow expansible chamber having a movable wall operatively connected to said first valve means for positioning the same,

thru said conduit, va first arestricted inlet passage connecting said fuel conduit and said rst`cham tocontrol said fuel ber, a restricted outlet passage for said chamber, second valve means in said outlet passage, passage means for conveying air for combustion purposes to said engine, means responsive to the quantity of air flowing thru said passage means to operate said second valve means andV thereby iiow in proportion to said air flow, throttle means for controlling the. flow of air thru said passage means, and an acceleration control unit comprising a casing, a pair of ilexible diaphragms extending laterally of said casing, a rigid Wall extending laterally of said casing between said diaphragms, said diaphragms and said wall dividing said casing into four expansible chambers, a rod connecting said diaphragme and extending thru said wall, restricted passage means connecting one of said four chambers to said restricted outlet passage, check valve means operative upon contraction of said one of said four chambers to close said restricted outlet passage between said rst chamber and said second valve means so that the pressure in said lirst chamber is then controlled bythe pressure in said one chamber and not by said second valve means, means connecting a second of said four chambers to said air passage means at a point downstream from said throttle means, means for venting a third of said four chambers to atmosphere so as to balance 'said' diaphragms against variations in atmospheric pressure, and means connecting the fourth of said four chambers to said first conduit between said iirst valve means and said metering restriction so as to balance said diaphragme against variations in the fuel'pressure there eX- isting.

15. A fuel supply system as in claim 9 including means responsive to the pressure in said first conduit between said first valve means and said metering restriction for controlling the rate of contraction of said second chamber cumulatively with said air pressure responsive means.

16. A fuel supply system for an internal combustion engine, comprising a first conduit for conveying combustion air to said engine, means associated with said conduit for producing two unequal air pressures Whose difference is a Ineasure of the rate of flow of air thru said conduit, means for supplying fuel under superatmospheric pressure, a second conduit for conveying fuel from said fuel supply means to said engine, a metering restriction in said second conduit effective to control the flow o fuel therethru as a function of the fuel pressure differential thereacross, a main valve for variably restricting said second conduit to control the pressure in the portion of said conduit between said valve and said restriction, an expansible chamber havinga movable Wall subject on its exterior surface to the fuel pressure in said portion of said second conduit, said Wall being operatively connected to said main valve for positioning the same, a restricted inlet passage connecting the interior oi said chamber to said second conduit, a restricted outlet passage connecting the interior of said chamber to a point maintained at a continuously lower pressure, second valve means for controlling said restricted outlet passage, means responsive to the difference of said air pressures for operating said second valve means, throttle meansl for controlling the iiow of air thru said first conduit, and' means operative as an incident to an opening movement of said throttle means to varyY the pressure in said chamber in a sense to. cause an opening movement of said main valve and: thereby to increase the fuel flow therethru.

12 17. A fuel supply system. foran internal combustionyengine, comprising' a first lconduit for conveyingA combustion-:air to said engine, means .associated with said conduit vfor producing two unequal air' pressuresivhose dilerence is a measure of therate of flow of air thru saidconduit,

Y*means iorsupplying fuel under superatmospheric pressure, a second conduit for conveying fuel from said fuel supply means to said engine, a metering restriction in said second conduit effective to control the flow of fuel therethru as a function ofthe fuel pressure, diierential thereacross, a main valve for variably restricting said second conduit to control the pressure in theportion of said Vconduit between said valve and said restriction, an expansible chamber having'a movable Wall subject on its exterior surface to the fuel pressure in said portion of said second conduit, said wall being operatively connectedto said main valve for positioning the same, a restricted inlet passage connecting the interior of said chamber to said second conduit, a restricted outlet passage connecting the interior of said chamber to a point maintained at a continuouslylower pressure, second valve means for controlling said restricted outlet passage, means responsive to the dilerence of said air pressures for operating said second valve means, throttle means for controlling the flow of air thru said rst conduit. and means operative as an incident to an opening movement -o said throttle means, to close said outlet passage and to supply additional fuel to said chamber so as to operate said main valve to increase the fuel flow therethru.

1B. In a carburetorv for an internal combustion engine, in combination, a source of fuel under superatmospheric pressure, a conduit for conveying fuel to said engine, valve means actuated solely by variations. in fuel pressure for controlling the flow of iuel through said conduit comprising a valve member, an expansible chamber having a movable Wall, al connection between said wall Yandfsaid valve member, a restricted fluid inlet'passage'to Vsaid chamber, a restricted nuid outlet passage from said chamber, means for varying the .effective area of said outlet passage to control the pressure in said chamber and thus the movements of said valve member, and pump means for supplying additional fluid to said chamber to control the pressure therein and the movements of said valve member independently of the area varying means.

sco'rT r. HUNT.

REFERENCES, CITED The vfollowing references are of record in the iile of'this patent:

UNITED STATES PATENTS Great Britain Jan. 2F', 1942 

